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Research Article Online first
Sensitive humidity sensor based on moisture-driven energy generation
Nano Research
Published: 07 March 2024
Downloads:53

The emergence of novel self-powered humidity sensors has attracted considerable attention in the fields of smart electronic devices and personal healthcare. Herein, self-powered humidity sensors have been fabricated using a moisture-driven energy generation (MEG) device based on asymmetric tubular graphitic carbon nitride (g-CN) films prepared on anodized aluminum (AAO) template. At a relative humidity (RH) of 96%, the MEG device can provide an open-circuit voltage of 0.47 V and a short-circuit current of 3.51 μA, with a maximum output power of 0.08 μW. With inherent self-powered ability and humidity response via current variation, an extraordinary response of 1.78 × 106% (41%–96% RH) can be gained from the MEG device. The possible power generation mechanism is that g-CN/AAO heterostructure can form ion gradient and diffusion under the action of moisture to convert chemical potential into electrical potential, evoking a connaturally sensitive response to humidity. Self-powered respiration monitoring device based on the sensor is designed to monitor human movement (sitting, warming up, and running) and sleep status (normal, snoring, and apnea), maintaining excellent stability during cumulative 12-h respiration monitoring. This self-powered humidity sensing technology has promising potential for extensive integration into smart electronic and round-the-clock health monitoring devices.

Research Article Just accepted
Triggering Triplet Excitons of Carbon Nanodots through Nanospace Domain Confinement for Multicolor Phosphorescence in Aqueous Solution
Nano Research
Available online: 07 February 2024
Downloads:26

Easy non-radiative decay property of long-lived triplet excitons in aqueous solution obstruct their applications in aquatic surroundings. Recently reported phosphorescence phenomena in aqueous solution have excited researchers enormously but achieving full-color water-soluble phosphorescent carbon nanodots (CNDs) is still a challenging issue. Herein, full-color phosphorescence of water-soluble CNDs has been demonstrated by triggering their triplet excitons through nanospace domain confinement, and Förster energy resonance transfer is used for further tuning phosphorescence range. The phosphorescence spans across most of the visible spectrum, ranging from 400 nm to 700 nm. In an aqueous solution, the CNDs exhibits blue, green, and red phosphorescence, lasting for approximately 6, 10, and 7 seconds, respectively. Correspondingly, the phosphorescence quantum yields are 11.85 %, 8.6 % and 3.56 %, making them readily discernible to the naked eyes and laying a solid foundation for practical application. Furthermore, phosphorescence flexible optical display and bioimaging have been demonstrated by using the multicolor CNDs-based nanomaterials, showing distinct superiority for accuracy and complete display and imaging in complex emission background.

Research Article Online first
Rational design multi-color-emissive chemiluminescent carbon nanodots in a single solvothermal reaction
Nano Research
Published: 30 January 2024
Downloads:50

Recently, the chemiluminescence (CL) induced by carbon nanodots (CDs) has intrigued researchers’ extensive interests in various applications due to its special light emission principle. However, the difficulty of synthesizing chemiluminescent CDs with full-spectrum emission severely hinders the further regulation of the CL emission mechanism. Herein, the multi-color-emissive chemiluminescent CDs are rational designed and further synthesized by regulating the sp2-hybrid core and sp3-hybrid surface from the citrate-ammonia molecular in a single solvothermal reaction. More experimental characterizations and density functional theory calculations reveal that the higher temperature can promote the crosslinking polymerization/carbonization of carbon core and the higher protonation of solvent can determine the core size of final CDs, resulting in the variant CL emission from molecular-, crosslinking- and core-states. Thus, the CL emission of the CDs can be further synthesized by tuning the luminescence chromophores in the formation process via regulating the temperature and solvent, enabling the applications of the CL CDs in illumination and information encryption. This study paves a new technology to understand the luminescence of CDs and affords an industry translational potential over traditional chemiluminescent molecular.

Research Article Issue
Cationic engineered nanodiamonds for efficient antibacterial surface with strong wear resistance
Nano Research 2024, 17 (3): 939-948
Published: 25 January 2024
Downloads:50

The spread of diseases caused by bacterial adhesion and immobilization in public places constitutes a serious threat to public health. Prevention of bacteria spread by the construction of an antibacterial surface takes precedence over post-infection treatment. Herein, we demonstrate an effective antibacterial surface with strong wear resistance by constructing cationic engineered nanodiamonds (C-NDs). The C-NDs with positive surface potentials interact effectively with bacteria through electrostatic interactions, where the C-NDs act on the phospholipid bilayer and lead to bacterial membrane collapse and rupture through hydrogen bonding and residual surface oxygen-containing reactive groups. In this case, bactericidal rate of 99.99% and bacterial biofilm inhibition rate of more than 80% can be achieved with the C-NDs concentration of 1 mg/mL. In addition, the C-NDs show outstanding antibacterial stability, retaining over 87% of the antibacterial effect after stimulation by adverse environments of heat, acid, and external abrasion. Therefore, an antibacterial surface with high wear resistance obtained by integrating C-NDs with commercial plastics has been demonstrated. The antibacterial surface with a mass fraction of 1 wt.% C-NDs improved abrasion resistance by 3981 times, with 99% killing of adherent bacteria. This work provides an effective strategy for highly efficient antibacterial wear-resistant surface, showing great practical applications in public health environments.

Research Article Issue
Highly sensitive humidity sensors based on hexagonal boron nitride nanosheets for contactless sensing
Nano Research 2023, 16 (7): 10279-10286
Published: 30 June 2023
Downloads:158

Humidity sensors with high sensitivity, rapid response, and facile fabrication process for contactless sensing applications have received considerable attention in recent years. Herein, humidity sensors based on hexagonal boron nitride (h-BN) nanosheets that are synthesized by a facile ultrasonic process have been fabricated, which display an ultrahigh sensitivity of 28,384% at 85% relative humidity (RH), rapid response/recovery time (3.0/5.5 s), and long-term stability in a wide humidity detection range (11%–85% RH), superior to most of the reported humidity sensors. The high sensitivity can be ascribed to the massive hydrophilic functional groups absorbed on the h-BN nanosheet surface. Benefiting from the high humidity sensing performances, contactless Morse code messaging and human writing and speech recognition have been demonstrated. This work demonstrates the great potential of the high-performance h-BN nanosheet-based humidity sensors for future contactless sensing devices.

Research Article Issue
Continuous synthesis of ultra-fine fiber for wearable mechanoluminescent textile
Nano Research 2023, 16 (7): 9379-9386
Published: 31 March 2023
Downloads:87

Continuous mechanoluminescence (ML) fibers and fiber-woven textiles have the potential to serve as new wearable devices for sensors, healthcare, human–computer interfacing, and Internet of Things. Considering the demands on wearability and adaptability for the ML textiles, it is essential to realize the continuous synthesis of fiber, while maintaining a desired small diameter. Here, we develop a novel adhere-coating method to fabricate ML composite fiber, consisting of a thin polyurethane (PU) core and ZnS:Cu/polydimethylsiloxane (PDMS) shell, with the outer diameter of 120 μm. By diluting PDMS to tune the thickness of liquid coating layer, droplets formation has been effectively prevented. The composite fiber exhibits a smooth surface structure and superior ML performances, including high brightness, excellent flexibility, and stability. In addition, a weft knitting textile fabricated by the continuous ML fiber can be easily delighted by manually stretching, and the ML fibers can emit visible signals upon human motion stimuli when woven into commercial cloth. Such continuous ultra-fine ML fibers are promising as wearable sensing devices for human motion detection and human–machine interactions.

Research Article Issue
Ultrasensitive broadband position-sensitive detector based on graphitic carbon nitride
Nano Research 2023, 16 (1): 1277-1285
Published: 31 August 2022
Downloads:82

As a typical two-dimensional material, graphitic carbon nitride (g-CN) has attracted great interest because of its distinctive electronic, optical, and catalytic properties. However, the absence of a feasible route toward large-area and high-quality films hinders its development in optoelectronics. Herein, high-quality g-CN films have been grown on Si substrate via a vapor-phase transport-assisted condensation method. The g-CN/Si heterojunction shows an obvious response to ultraviolet–visible-near infrared photons with a responsivity of 133 A·W−1, which is two orders of magnitude higher than the best value ever reported for g-CN photodetectors. A position-sensitive detector (PSD) has been developed using the lateral photovoltaic effect of the g-CN/Si heterojunction. The PSD shows a wide response spectrum ranging from 300 to 1,100 nm, and a position sensitivity and rise/decay time of 395 mV·mm−1 and 3.1/50 μs, respectively. Moreover, the application of the g-CN/Si heterojunction photodetector in trajectory tracking and acoustic detection has been realized for the first time. This work unveils the potential of g-CN for large-area photodetectors, and prospects for their applications in trajectory tracking and acoustic detection.

Research Article Issue
High-performance solar-blind photodetector arrays constructed from Sn-doped Ga2O3 microwires via patterned electrodes
Nano Research 2022, 15 (8): 7631-7638
Published: 19 May 2022
Downloads:71

Ga2O3 has been regarded as a promising material for solar-blind detection due to its ultrawide bandgap and low growth cost. Although semiconductor microwires (MWs) possess unique optical and electronic characteristics, the performances of photodetectors developed from Ga2O3 MWs are still less than satisfactory. Herein, we demonstrate high-performance solar-blind photodetectors based on Sn-doped Ga2O3 MWs, possessing a light/dark current ratio of 107 and a responsivity of 2,409 A/W at 40 V. Moreover, a 1 × 10 solar-blind photodetector linear array is developed based on the Sn-doped Ga2O3 MWs via a patterned-electrodes method. And clear solar-blind images are obtained by using the photodetector array as the imaging unit of a solar-blind imaging system. The results provide a convenient way to construct high-performance solar-blind photodetector arrays based on Ga2O3 MWs, and thus may push forward their future applications.

Research Article Issue
Negative differential friction coefficients of two-dimensional commensurate contacts dominated by electronic phase transition
Nano Research 2022, 15 (6): 5758-5766
Published: 04 April 2022
Downloads:44

Friction force (f) usually increases with the normal load (N) macroscopically, according to the classic law of Da Vinci–Amontons (f = µN), with a positive and finite friction coefficient (µ). Herein near-zero and negative differential friction (ZNDF) coefficients are discovered in two-dimensional (2D) van der Waals (vdW) magnetic CrI3 commensurate contacts. It is identified that the ferromagnetic–antiferromagnetic phase transition of the interlayer couplings of the bilayer CrI3 can significantly reduce the interfacial sliding energy barriers and thus contribute to ZNDF. Moreover, phase transition between the in-plane (px and py) and out-of-plane (pz) wave-functions dominates the sliding barrier evolutions, which is attributed to the delicate interplays among the interlayer vdW, electrostatic interactions, and the intralayer deformation of the CrI3 layers under external load. The present findings may motivate a new concept of slide-spintronics and are expected to play an instrumental role in design of novel magnetic solid lubricants applied in various spintronic nano-devices.

Research Article Issue
Fabry-Perot interference and piezo-phototronic effect enhanced flexible MoS2 photodetector
Nano Research 2022, 15 (5): 4395-4402
Published: 06 December 2021
Downloads:75

Flexible photodetectors (PDs) are indispensable components for next-generation wearable electronics. Recently, two-dimensional (2D) materials have been implemented as functional flexible optoelectronic devices due to their characteristics of atomically thin layers, excellent flexibility, and strain sensitivity. In this work, we developed a flexible photodetector based on MoS2/NiO heterojunction, and Fabry-Perot (F-P) and piezo-phototronic effect have been employed to enhance the responsivity (R) and external quantum efficiency (EQE) of the devices. The F-P effect is utilized to improve the optical absorption of the MoS2, resulting in an enhancement in the photoluminescence (PL) of monolayer MoS2 and the EQE of the photodetector by 30 and 130 times, respectively. The flexible photodetector exhibits an ultrahigh detectivity (D*) of 2.6 × 1014 Jones, which is the highest value ever reported for flexible MoS2 PDs. The piezo-potential of monolayer MoS2 decreases the valence band offset at the interface of MoS2/NiO, which increases the transfer efficiency of the photon-generated carriers significantly. Under 1.17% tensile strain, the R of the flexible photodetector can be enhanced by 271%. This research may provide a universal strategy for the design and performance optimization of 2D materials heterostructures for flexible optoelectronics.

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